Electromagnetic switch



2 Sheets-Sheet 1 Filed NOV. 8, 1952 INVENTOR. Era/Z FM%eZ ZZ/Zg.

, 77' oF/VEK Aug. 23, 1955 E. F. MEKELBURG ELECTROMAGNETIC SWITCH 2 Sheets-Sheet 2 Filed Nov. 8, 1952 United States Patent 2,716,171 Patented Aug. 23, 1955 fice ELECEROhKASNETKC SWX'ECH gan Application November 3, 1952, Serial No. 319,536

'7 Claims. (CL Edd-87) This invention relates to an electromagnetically operated electric switch operating with a predetermined time delay after energization.

One object of the present invention is the provision of an electromagnetically operated electric switch having adjustably timed operation after energization in which a simplified construction provides accurate constant timing periods.

Another object of the invention is the provision of an electromagnetic switch in accordance with the preceding object incorporating a variable reluctance magnetic circuit in which the reluctance of the magnetic circuit is rapidly changed from a switch inoperative to a switch operative value and in which the period from energization of the switch to the change in the value of reluctance is accurately timed.

Another object of the invention is the provision of a time-delay electromagnetic switch of the movable core, variable reluctance type in which movement of the core through the critical operating zone occurs rapidly without substantial retardation and in which the time delay is a period between the energization of the switch and the initiation of substantial core movement.

Other objects and features of the invention will be readily apparent to those skilled in the art from the specification and appended drawings illustrating certain preferred embodiments in which:

Figure 1 is a front elevational view of an electric switch according to the present invention.

Figure 2 is a side elevational view of the electric switch according to the present invention, with portions broken away to show parts in section.

Figure 3 is a detail sectional view on the line 1IIlII of Figure 2.

Figure 4 is a view similar to Figure 2 and showing the parts in closed circuit position.

Figure 5 is a partial rear elevational view showing the metering cap.

The electric switch according to the present invention, as specifically shown in the drawing, is mounted upon a supporting plate 1 of insulating material and includes a stationary contact 2 carried by a finger 3 removably mounted by a stud 4 upon a support 5 mounted on the front face of plate 1 by a stud 6. Also mounted on the front face of the plate 1 and beneath the support 5 is an L-shaped bracket 7 of magnetic material having a hole through its vertical leg in which is secured, as by spinning, a cylindrical tube 8 of non-magnetic material having its forward end closed by a plug 9 of magnetic material. In front of and mounted on the plug 9 by a stud 11 is a core cap 12 also of magnetic material. The horizontal leg of the bracket 7 has riveted thereto a plate 13 having a pair of depending legs 14 and 15 and a pair of forwardly extending fingers 16 and 17.

An armature plate 18 of magnetic material is provided with a pair of slots 19 and 21 in its opposite lower side edges in which are received the fingers 16 and 17 to provide a pivotal mounting for the armature plate 18. The

lower edge of the armature 18 is provided with a slot 22 through which extends a pin 23 provided adjacent its outer end with a cross pin 24 received within a transverse notch 25 in the front face of the armature 18. The pin 23 extends through a pair of guide openings in the depending legs 14 and 15 and carries therebetween a spring 26 received within a pair of opposed cups 27, one of which is backed by a pin 28 on the hinge pin 23 and the other of which is backed by the leg 14 so that spring 26 biases the pin 23 toward the right as viewed in Figure l, and therefore biases the armature 18 counterclockwise into the open position as therein shown.

On the front face of the armature 18 is mounted a contact finger support 29 having a contact finger 31 rigidly attached thereto, the finger 31 carrying a movable contact 32 cooperating with stationary contact 2. The support 29 is pivoted on the armature 18 at the cooperating nose and groove 33 and is biased toward the armature by spring 34 mounted upon a pin 35 rigid with the armature 18 and extending freely through the support 29 and finger 31, the spring 34 being mounted between a pair of cups 36, one bearing against the front face of the contact finger, the other against a stop pin in the pin 35.

Within the non-magnetic tube 8 is disposed a movable core 37 having an opening 38 in its front face receiving a compression spring 39 biasing the core toward the right as viewed in Figure 1 into its position of greatest magnetic reluctance, the magnetic circuit for the switch being formed by bracket 7, movable core 37, plug 9, core cap 12 and armature 18. The back face of the core 37 is provided with a conical depression bounded by the surface 41 against which a conical washer 42 clampingly deforms a flat washer 43 of elastic material such as Vinyiite" or silicone rubber. The washer 42 is firmly seated against the rear face of the elastic washer 43 to draw it within the conical depression in the core by means of a stud 44, the washer 43 thereby assuming a suction cup shape, as shown more particularly in Figure 4. Surrounding the tube 8 is an energization coil 49.

Upon the rear face of the plate 1 is mounted a metering cap assembly 45 comprising a body portion 46 having an inner cup-shaped opening 47 whose base provides a seating face with which the suction cup 43 cooperates. The base of the cup is provided with an opening 48 communieating with a passageway 49 leading to a metering passageway 51 under the control of a metering screw 52, communication to the exterior being established from metering passage 51 through orifice 53.

In the specific embodiment shown in the drawing, the orifice 53 is shown in communication with the exterior air but it is understood that communication thereto may be arranged through a conventional filter pad or that the orifice 53 may be connected to the interior of the tube 8 and the device sealed to provide a closed gaseous chamber sealed from outside air. These arrangements for metered air in dash pots are not, in themselves, new, but are contemplated with the combination of this invention where necessary or desired.

In the electromagnetic switch of this invention, it will be seen that there are provided two air gaps in the magnetic circuit when the switch is in the open position of Figure 1, one between the core 37 and the plug 9 and the other between the core cap 12 and the armature 18. With the core 37 in the retracted position of Figure 1, the reluctance of the magnetic path is such that with energization of the coil 40 there is insufficient magnetic pull between the core cap and armature to move the latter toward closed position.

In the deenergized position of the switch, the core 37 is pushed to the right by the spring 3% and the suction cup formed by the elastic washer 43 is engaged with the seating face of the dash pot assembly formed by the base of the cup 47. When the coil 40 is energized, the core 37 will be electromagnetically biased toward the left into engagement with the magnetic plug 9 and against the bias of the spring 39 which is not sufficiently strong to oppose movement of the core. The vacuum which is produced under the suction cup will, however, prevent movement of the core 37 until this vacuum is reduced by the passage of air from orifice 53 through metering passage 51, passageway 49 and opening 48 into the interior of the suction cup. The time interval after energization of the coil 4%) when suction cup 4-3 will be released will depend upon the setting of the metering screw 52 and this controls the time delay between the energization of the operating coil and the operation of the relay. It will be seen that actual physical movement of the core 37 while under the control of the vacuum cup 43 and the metering passage is quite short and at the time the suction cup 43 is released from the base of the cup 47 a considerable air gap still exists between the core 37 and plug 9.

From the moment of release, the core 37 is entirely freed from retarding control and it will move very rapidly into engagement with the plug 9. Just before, or when, the core 37 engages the plug 9, the magnetic reluctance of the magnetic circuit becomes sufficiently low so that the magnetic fiux at the core cap 12 will pull the armature 13 into engagement, thus engaging movable contact 32 with the stationary contact 2.

Upon deenergization of the coil 48, the armature and contact finger will move to open position without delay as in the case of a standard electromagnetic switch. Upon this deenergization, the core 37, which was in the position of Figure 4 attracted to the plug 9, will be moved toward the right under the bias of spring 39 into the position of Figure 2 with the suction cup 43 engaged with the seating surface formed by the base of the cup 47 and in position to effect the time delay previously described.

With the electric switch according to the present invention, it will be seen that the change in magnetic reluctance at the time the armature is picked up is effected very rapidly as the core 37 is then moving freely without retardation under the differential between the magnetic force thereon and the bias of the spring 39. During this movement, the suction has been entirely released and the dash pot assembly 45 and meter passage 51 have no effect whatsoever upon the movement of the core. Therefore, it is apparent that the tripping point and the time delay are substantially independent of variations in the magnetic reluctance since the change from insufficient magnetic force on the armature 11$ to a sufficient magnetic force may occur over a relatively wide physical space without change in timing since the change in reluctance is effected without delay, the timing period occurring only at the beginning of the stroke of the core 37 and its further movement being thereafter without retardation.

The very short initial stroke of the core 37 through which timing occurs keeps a constant tripping point for the electric switch so that the timing period once adjusted remains constant and accurate; or, stated again, the movable core is delayed only over a very short stroke in a non-critical zone with respect to the reluctance of the magnetic circuit and the movement of the core in the critical zone of the magnetic reluctance where variations could occur is effected rapidly and without retardation so that variations in the physical dimensions at which the reluctance decreases to a point where the armature is picked up become immaterial, the change being effected through the entire possible variable zone without delay.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims.

What is claimed is:

l. In a time delay electromagnetic switch, a stationary Contact, a movable contact cooperating with said stationary contact to open and close the circuit through the switch, a movable armature controlling said movable contact, a magnetic circuit for said armature including a pole piece for attracting said armature and a movable core biased away from said pole piece to form a second air gap between itself and the armature in the open position of the switch, an energizing coil for said magnetic circuit for attracting said core and armature toward the pole piece, a suction cup cooperating with said core to delay the initial movement thereof toward energized position, and means metering the passage of air to said suction cup to adjust the time delay in the release thereof, the reluctance of the combined air gaps being so high that there is insufficient magnetic pull upon energization of said coil to move the armature into ciosed position until the core has been released by the suction cup for movement toward the pole piece to reduce the air gap therebetween.

2. In a time delay electromagnetic switch, a stationary contact, a movable contact cooperating with said stationary contact to open and close the circuit through the switch, a movable armature controlling said movable contact, a magnetic circuit for said armature including a pole piece for attracting said armature and a movable core biased away from said pole piece to form a second air gap between itself and the pole piece in addition to the air gap between the pole piece and the armature in the open position of the switch, an energizing coil for said magnetic circuit for attracting said core and armature toward the pole piece, a suction cup cooperating with said core to delay the initial movement thereof toward energized position, and means metering the passage of air to said suction cup to adjust the time delay in the release thereof, the reluctance of the combined air gaps being so high that there is insufiicient magnetic pull upon energization of said coil to move the armature into closed position until the core has been released by the suction cup for movement toward the pole piece to reduce the air gap therebetween, the delay in movement of said core being effective through only a short stroke in the initial movement thereof and the suction cup releasing the core entirely at the end of said short stroke to permit unretarded movement of the core thereafter whereby the decrease in magnetic reluctance to an armature operating value occurs without delay over the entire range of possible variation.

3. In a time delay electromagnetic switch, a stationary contact, a movable contact cooperating with said stationary contact to open and close the circuit through the switch, a movable armature controlling said movable contact, a magnetic circuit for said armature including a pole piece for attracting said armature and a movable core biased away from said pole piece to form a second air gap between itself and the pole piece in addition to the air gap between the pole piece and the armature in the open position of the switch, the reluctance of the combined air gaps being so high as to prevent pick-up of the armature, an energizing coil for said magnetic circuit for attracting said core and armature toward the pole piece, time delay means retarding the initial movement only of the core while the magnetic reluctance is substantially larger than the maximum value permitting pick-up of the armature, said teans releasing the core for unretarded movement after a predetermined time delay so that the change in magnetic pick-up from considerably below a minimum operating value to an operative value is effected Without delay through the entire possible variable range.

4. In a time delay electromagnetic switch, a stationary contact, a movable contact cooperating with said stationary contact to open and close the circuit through the switch, a movable armature controlling said movable contact, a magnetic circuit for said armature including a pole piece for attracting said armature and a core movable relative to said pole piece to form a second air gap between itself and the pole piece in addition to the air gap between the pole piece and the armature in the open position of the switch, the reluctance of the combined air gaps being so high as to prevent pick-up of the armature, an energizing coil for said magnetic circuit for attracting said core and armature toward the pole piece, a suction cup mounted on the back face of the core, a seating surface cooperating with said suction cup to seal a vacuum therein means biasing said core away from said pole piece and said suction cup against said seating face, and adjustable means metering the passage of air into the suction cup to determine the release point thereof, said suction cup leaving the seating surface after energizetion of said coil while the air gap between the core and the pole piece is substantial and the magnetic force insufficient to attract the armature whereby the change from substantially below the minimum operating value of magnetic force to an operative value is eflected without delay.

5. In a time delay electromagnetic switch, a stationary contact, a movable contact cooperating with said stationary contact to open and close the circuit through the switch, a movable armature controlling said movable contact, a magnetic circuit for said armature including a pole piece for attracting said armature and a core movable relative to said pole piece to form a second air gap between itself and the pole piece in addition to the air gap between the pole piece and the armature in the open position of the switch, the reluctance of the combined air gaps being so high as to prevent pick-up of the armature, an energizing coil for said magnetic circuit for attracting said core and armature toward the pole piece, a conical depression in the back face of the core, a conical washer cooperating with said depression, a flexible washer disposed in said depression beneath said conical washer so as to be formed into a suction cup projecting from the back face of the core, a seating surface cooperating with the suction cup, means biasing the core away from the pole piece and the suction cup into engagement with the seating surface, and adjustable means for metering the passage of air into the space within the suction cup while it is engaged with its seating surface.

6. In an electromagnetic switch, a stationary contact, a movable contact cooperating with said stationary contact to control the circuit through the switch, a magnetic armature for controlling the operation of the movable contact,

a magnetic circuit for controlling the position of the armnture and including a magnetic plate spaced from said armature, a tube of non-magnetic material mounted in said plate, a magnetic pole piece mounted on the end of said tube remote from said plate, a core of magnetic material within said tube movable relative to said pole piece to form an air gap therebetween, spring means biasing said core away from said pole piece, an operating coil about said tube for energizing the magnetic circuit, said spring means being insufficient to prevent movement of said core toward said pole piece when said coil is energized, the magnetic reluctance of the magnetic path with the combined air gaps between the core and pole piece and pole piece and armature being sufficient to prevent pull-in of the armature until the movable core has substantially reduced the magnetic gap between itself and the pole piece, and time delay means for delaying only the initial stroke of the core in the range of space where the magnetic reluctance is considerably above the maximum at which armature attraction occurs whereby the timing of the delay period will be independent of variations in the armature pick-up point since the change in magnetic pull adjacent that point will be efi'ected substantially without delay.

7. In an electromagnetic switch, a stationary contact, a movable contact cooperating with said stationary contact to control the circuit through the switch, a magnetic armature for controlling the operation of the movable contact, a magnetic circuit for controlling the position of the armature and including a magnetic plate spaced from said armature, a tube of non-magnetic material mounted in said plate, a magnetic pole piece mounted on the end of said tube remote from said plate, a core of magnetic material within said tube movable relative to said pole piece to form an air gap therebetween, spring means biasing said core away from said pole piece, an operating coil about said tube for energizing the magnetic circuit, said spring means being insufficient to prevent movement of said core toward said pole piece when said coil is energized, the magnetic reluctance of the magnetic path with the combined air gaps between the core and pole piece and pole piece and armature being sufficient to prevent pull-in of the armature until the movable core has substantially reduced the magnetic gap between itself and the pole piece, a suction cup restraining initial movement of the core from its position remote from the pole piece,

means for adjustably metering air into said suction cup 7 References Cited in the file of this patent UNITED STATES PATENTS 1,730,688 Rippl Oct. 8, 1929 2,077,295 Whitney Apr. 13, 1937 2,489,381 Lindahl Nov. 29, 1949 

